The makeshift encampment is all that remains of a once-sprawling "caliphate" declared in 2014 over large swaths of Syria and neighbouring Iraq. The SDF and coalition warplanes have rained fire on the enclave since last Sunday, blitzing more than 4,000 IS fighters and family members into surrender.

US-backed forces have reduced daytime airstrikes and shelling to allow for more exits from the last jihadist bastion. But AFP journalists at an SDF post inside Baghouz heard sporadic rounds of mortar fire Saturday and an SDF spokesman said clashes were ongoing.

"Clashes broke out again last night and have continued since," SDF spokesman Adnan Afrin said. "There have so far been no surrenders (today) and there's no sign they are giving up," the spokesman told AFP.

An SDF statement the latest fighting broke out after the Kurd-led force attacked IS positions inside Baghouz. Around 32 jihadists, including at least four senior IS figures, were killed in battle, it said.

On Friday, IS launched three suicide attacks outside Baghouz, killing six people among those fleeing the village near the Iraqi border. They were the latest casualties in Syria's devastating civil war as it entered its ninth year with 370,000 dead.

"Daesh has proven to demonstrate a reckless disregard for human life and continues to be a global threat," the US-led coalition said late Friday, using an Arabic acronym for IS. "We stand by our SDF partners as they fight to liberate that last Daesh-held territory," it said on Twitter.

Die-hard IS fighters have unleashed a wave of suicide bombings over the past week to impede the SDF advance. It remains unclear how many fighters and civilians remain inside Baghouz.

More than 61,000 people have streamed out of IS-held territory since December, the Britain-based Syrian Observatory for Human Rights says, a tenth of them suspected jihadists. The exodus has sparked a humanitarian crisis in Kurdish-run camps for the displaced further north where civilians have been transported.

These include the wives and children of alleged foreign jihadists, hundreds of whom are being held by the Kurdish forces. Around 3,000 people arrived at Al-Hol camp from Baghouz over the past two days, pushing the camp's population to over 69,000, the International Rescue Committee (IRC) said Saturday.

The UN said most of the new arrivals "show clear signs of distress, fatigue, malnutrition and require some form of medical care or attention". According to the IRC and UN, around 122 people, mainly children, have died en route to the camp or shortly after arriving since December.

"There is an urgent requirement for funding to continue health and nutrition interventions in the camp," the UN said. At the height of its brutal rule, IS controlled a stretch of land in Syria and Iraq the size of the United Kingdom.

The total capture of the Baghouz camp by the SDF would mark the end of the cross-border "caliphate" it proclaimed more than four years ago. But beyond Baghouz, IS retains a presence in eastern Syria's vast Badia desert and sleeper cells in the northeast. The jihadists have continued to claim deadly attacks in SDF-held territory in recent months.